Synchronized normal and malignant human cells, mouse cells and man- mouse hybrid cells carrying different amounts of human genetic material, will be used to investigate the dynamics of transcription and/or translation during the cell cycle. Adequate populations of synchronized cells will be obtained mainly through stockpiling mitotic cells collected by selective detachment in a continuous culture system. Quantitative studies for a number of enzyme proteins, known to be coded by autosomal or X-linked genes in Man will be performed by immunoprecipitations, enzyme assay or cellogel electrophoresis followed by densitometric tracing. DNA-RNA- hybridization (Cot analysis) under conditions of large DNA excess will be used to evaluate the relative amounts of repetitive and non- repetitive nuclear RNA produced at given times of the cell cycle. These studies are expected to yield (1) Data on the pattern of translation of specific human genes that can be correlated to the genes' linkage relationship, their location on a chromosome and the structural organization of that chromosome. (2) Data on the pattern of transcription and translation of human nuclear RNA's at the level of a single human chromosome or part of it. (3) Possible clues for further studies on the molecular biology of malignancy by comparing the above parameters in normal and malignant cells (diploid fibroblasts or lymphoblasts versus tumor derived cell lines).